The current study examined the impact of BMI and illicit drug use on the ability to inhibit prepotent behaviors. Participants (n = 290) completed surveys and behavioral tasks: theStroop Test and Go/No-Go. After controlling for age and gender, higher BMI was an independent predictor of poorer performance in both the Stroop and Go/No-Go tasks. Illicit drug use was a predictor of poorer Stroop performance only. However, post hoc analyses showed that illicit drug use significantly impacted Go/No-Go performance in normal weight participants. We conclude that elevated BMI and illicit drug use are predictive of poorer performance on executive functioning tasks that require inhibition of a prepotent response.